Hot-rolled straight-web steel sheet pile

ABSTRACT

The hot-rolled straight-web steel sheet pile comprises a straight web delimited on each longitudinal side respectively by an interlock strip. The web has a rolled-in taper which is designed in such a way that, in a tensile test of two samples from this sheet pile which are connected by means of their interlock strips, the web is deformed plastically in the region of this taper before a failure of the interlock connection can occur. The rolling of such a sheet pile, which is distinguished in cellular cofferdams by a high plastic deformation capacity, can take place by means of slightly modified standard rolls and consequently requires no major investment.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a hot-rolled straight-web steel sheetpile, in particular for the construction of cellular cofferdams.

BACKGROUND OF THE INVENTION

The first hot-rolled straight-web steel sheet piles, also referred to asstraight sheet piles, were already in use in the USA at the end of the19th century. In Europe, these straight sheet piles have been rolledsince the thirties of the 20th century. They comprise a straight webwhich lies in the wall axis and is delimited on each longitudinal sideby an interlock strip. The individual straight sheet piles can beconnected into a continuous sheet pile wall by means of these interlockstrips.

Straight sheet piles are used particularly for the construction ofcellular cofferdams without internal anchoring. Depending on the shapeof the cells, a distinction is made between circular or straightcellular cofferdams. In the U.S.A., straight sheet piles have also beenused for the construction of so called “open cells” (see, for example,U.S. Pat. No. 6,715,964). Closed and open cells are designed in such away that the loads originating from the filling and water overpressureproduce in the straight sheet piles only tensile stress in the directionof an horizontal wall axis.

In the dimensioning of the straight sheet piles for such cellularcofferdams, the stress (for example, the ring tensile force determinedby means of the “boiler formula”) is compared with the sheet pileresistance. The latter is obtained, according to EN 1993-5, as theminimum arising from a failure in the interlock and a creep (i.e. aplastic deformation) in the web.

However, the manufacturer selects the steel quality for the webtraditionally in such a way that the following condition is fulfilled:(f _(y) ·t)/S ₁ >R/S ₂ →f _(y)>(R·S ₁)/(t·S ₂)  (1)in which:f_(y)=the nominal yield point;t=the web thickness;R=the minimum interlock tensile strength guaranteed by the manufacturer(for example, R=5500 kN/m);S₁=a safety coefficient for the creep in the web;S₂=a safety coefficient for the failure in the interlock;the safety coefficients being different for the two types of failure,for example:S₁=1.0 (creep in the web);S₂=1.25 (failure in the interlock).

Adhering to the condition (1) given above ensures that the creep in theweb will never be critical under tensile load on the straight sheetpiles, that is to say that only the minimum interlock tensile strength Rguaranteed by the manufacturer has to be respected. As a result, afailure of a straight sheet pile connection is almost alwaysattributable to a breaking-open of an interlock connection.

A breaking-open of an interlock connection in the cell wall of acofferdam cell causes a discontinuity in the absorption of the ringtensile forces. This results in a gap in the cell wall, which becomesenlarged and through which the soil filling of the cofferdam cell isflushed away. Without sufficient soil filling, however, the cofferdamcell can no longer withstand the loads originating from the wateroverpressure, which will inevitably result in a failure of thecofferdam.

Almost all straight sheet piles have symmetrical interlock strips of the“thumb and finger” type which, rotated through 180°, hook together withone another. In the case of two interlock strips locked together, thetwo thumbs engage one behind the other, the fingers respectivelysurrounding the thumb of the opposite interlock strip (see FIG. 1). Afailure of such an interlock connection takes place either due to thetearing-off of the thumb subjected to tensile stress or due to theopening or breakage of the finger subjected to bending stress.

For reasons of cost, all manufacturers of straight sheet piles have intheir standard delivery range only three to four straight sheet pileswhich differ from one another essentially in the thickness of their web.As a rule, web thicknesses of 11 to 13 mm are implemented in suchstraight sheet piles. The selection of the steel quality then determinesthe minimum interlock tensile strength of the web, wherein, as a rule,values of 2000-4000 kN/m being ensured. New high-strength steels, suchas, for example, the steel S 460 GP, make it possible to ensure even aminimum interlock tensile strength of 5500 kN/m. Since an increasedsteel quality also leads to an increase in the yield point in the web,it is always warranted that the condition (1) remains fulfilled. It willalso be appreciated in this context that straight sheet piles with athicker web have, as a rule, a higher minimum interlock tensilestrength, since, during the rolling of a thicker web, the parts of theinterlock which are critical for the interlock tensile strength can alsobe rolled more thickly.

It sometime happens that the manufacturer cannot achieve the minimuminterlock tensile strength required for the construction project withstraight sheet piles from the standard delivery program. For reasons ofcost, however, a manufacturer is hardly prepared to roll specialstraight sheet piles for individual construction projects. In suchinstances, it is known to increase the minimum interlock tensilestrength of webs from the standard delivery program in that, startingfrom an existing calibration, the “calibre” is opened further during therolling operation, that is to say the gap set between the upper andlower roll is slightly increased. As a result, not only does the webbecome slightly thicker, but the parts of the interlock which arecritical for the interlock tensile strength are also of stronger designand consequently afford higher resistance. Such a method is described,for example, in JP55138511. It should be noted that this procedure alsoensures that the condition (1) remains fulfilled.

For the purpose of increasing the interlock tensile strength, it haslikewise been proposed to vary the geometry of the interlock strips(see, for example, JP56020227). However, for this purpose themanufacturer would have to invest in new rolls. Furthermore, he wouldsubsequently have to include in his delivery program two differentinterlock types for straight sheet piles, which does not exactlysimplify the logistics. For both reasons, the manufacturers of straightsheet piles are therefore hardly prepared to follow this path.

It has also been known for a long time that straight sheet piles mayalso be exposed to high dynamic loads in specific cofferdams. The wallsof the cells are, for example, rammed by ships and, in the case ofspring tides and storm tides, are exposed to the impact of heavy driftflotsam. Moreover, many cofferdams are also erected in earthquake zones.For such dynamic load situations, the straight sheet piles wouldactually have to be designed in a completely different way fromhitherto. Thus, for example, it would have to be ensured that thestraight sheet piles can absorb substantially higher deformation energythan hitherto before the failure of an interlock connection occurs.However, since it has been assumed that major investments are requiredfor the production of such a completely new straight sheet pile, nomanufacturer has hitherto put on the market a straight sheet pile whichis designed particularly for the dynamic load situations mentionedabove.

The present invention is based on the surprising finding that a straightsheet pile from the standard delivery range of a manufacturer can bemodified at very low outlay in such a way that it is substantially moresuitable for the absorption of dynamic stresses.

BRIEF SUMMARY OF THE INVENTION

According to the present invention, this object is achieved in that ataper is rolled into the web of the straight sheet pile and designed insuch a way that, in a tensile test of two samples from this sheet pile,which are connected by means of their interlock strips, the web isdeformed plastically in the region of this taper before a failure of theinterlock connection can occur. It will be appreciated that by simplyrolling a taper into the web, which can be achieved by means of an onlyslightly modified set of rolls used for rolling straight sheet piles ofthe standard program, i.e. without major investment in new roll stands,a straight sheet pile can be produced which, in contrast to knownstraight sheet piles, has a pronounced plastic work capacity in a sheetpile wall. Owing to this pronounced plastic work capacity, a sheet pilewall built with straight sheet piles according to the invention issubstantially more suitable for the absorption of dynamic stresses andcan be used particularly advantageously in cofferdams which are exposed,for example, to the following risks: ramming by ships, the impact ofheavy drift flotsam during storm tides and spring tides, and alsoearthquakes. In the cell wall, the webs of the sheet piles according tothe present invention can absorb a significant deformation energy undersuch loads, without a breaking-open of an interlock connectionoccurring.

In order to achieve the desired effect, the web is preferably to bedesigned for a nominal failure load which is less than 90% of theguaranteed minimum tensile strength of the interlock strips. In atensile test of two samples from this sheet pile which are connected bymeans of their interlock strips, a plastic displacement distance of atleast 1% of the overall width of the sheet pile is then to be measuredfor the web.

The taper is preferably to be designed symmetrically with respect to thecenter line of the web, so that it has the same distance from bothinterlock strips. It advantageously forms a central portion with a widthB and with a constant thickness t, wherein t is the minimum thickness ofthe web. The width B preferably amounts to between 5% and 80% of theoverall width W of the web. Good results are normally achieved even witha width B of between 30 and 100 mm. Alternatively, the thickness of thetaper may decrease continuously as far as the center line of the web,and the minimum thickness of the web may then be achieved only on thecenter line of the web.

The web advantageously has its maximum thickness in the connectionregion of the interlock strips. It advantageously has, for example,along each interlock strip a portion with a width b₀ and with a constantthickness t₀, t₀ being the maximum thickness of the web. Normally, t₀will amount to 13 to 14 mm.

The taper advantageously has a convexly cylindrical surface with aradius R₁, which has adjoining it towards the center line of the web aconcavely cylindrical surface with a radius R₂, wherein R₂ issubstantially larger than R₁, and is larger by a multiple than thenominal width of the sheet pile.

Further features and advantages of the invention may be derived from thefollowing description of a preferred embodiment of the invention and theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings show a preferred, but not exclusive embodimentof the invention, wherein:

FIG. 1 is a cross section through three hooked-together straight-websteel sheet piles from the standard delivery program of a manufacturer;

FIG. 2 shows a cross section through a straight-web steel sheet pileaccording to the invention, only the left half of the sheet pile beingshown; and

FIG. 3 is a graph which reproduces the load/displacement curves for astandard straight sheet pile and for two types of straight sheet pilesaccording to the invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows hot-rolled straight-web steel sheet piles 10′₁, 10′₂ and10′₃, such as have been put on the market for decades by variousmanufacturers. Such a straight sheet pile 10′₁ comprises a straight web12′ and two symmetrical interlock strips 14′₁, 16′₁. The latter are ofthe “thumb and finger” type and delimit the web 12′ on its twolongitudinal sides.

The dimensions of such a straight sheet pile are basically defined, asshown in FIG. 1: the nominal width of the straight sheet pile 10′₁ beingdesignated by “L”, the width of its web by “W” and the thickness of itsweb by “t”. Straight sheet piles from the current delivery program ofthe manufacturers have, for example, a nominal width of 500 mm, a webthickness of 11 to 13 mm and a delivery length of more than 30 m.

As is evident from FIG. 1, the straight sheet piles 10′ are arranged,alternately rotated through 180°, in a sheet pile wall and are hookedtogether with their interlock strips 14′, 16′. In the case of twohooked-together interlock strips 14′₁, 14′₂, the two thumbs 18′₁, 18′₂engage one behind the other, the fingers 20′₁, 20′₂ respectivelysurrounding the thumbs 18′₂, 18′₁ of the opposite interlock strip.

Such straight sheet piles are used particularly for the construction ofcellular cofferdams without internal anchoring. A distinction is madebetween circular or straight cellular cofferdams, depending on the shapeof the cells. In the U.S.A., such straight sheet piles have also beenused for the construction of so called “open cells” (see, for example,U.S. Pat. No. 6,715,964). These straight sheet piles are subjected totensile stress primarily in the direction of the horizontal cell extent.As already mentioned in the introduction, all known straight sheet pilesare designed such that no plastic deformation of the web occurs untilthe minimum interlock tensile strength guaranteed by the manufacturer isreached, that is to say until the failure of an interlock connection.

FIG. 2 shows the left half of a straight sheet pile 10 according to theinvention. Like the known straight sheet piles from FIG. 1, the latterlikewise comprises a substantially straight web 12 and two symmetricalinterlock strips of the “thumb and finger” type which delimit the web 12on its two longitudinal sides. Reference symbol 22 designates themid-plane of sheet pile 10 which at the same time is also a plane ofsymmetry of the sheet pile 10. The straight sheet pile 10 has the samewidth and the same interlock strips as the straight sheet piles 10′. Web12 lies on axis A that extends through interlocks 14. In the illustratedembodiment, axis A is also the neutral axis of web 12.

In contrast to the above-described standard straight sheet piles 10′ ofFIG. 1, however, the sheet pile 20 of FIG. 2 is designed in such a waythat the nominal failure load of the web is less than 90% of the minimumtensile strength of the interlock strips, so that, in a tensile test oftwo sheet piles connected by means of their interlock strips 14, the webis deformed plastically before the interlock strips 14 can give way.This is achieved in that tapered portions 26 are rolled into the web 12,so that the web 12 has a central web portion 24 with a reduced thicknessthat is deformed plastically before a failure of an interlock connectioncan occur.

Dimensioning Example of the Novel Sheet Pile:

The straight sheet pile shown was designed for a minimum interlocktensile strength of R=6000 kN/m. In order to achieve this relativelyhigh minimum interlock tensile strength, a steel quality S 460 GP with anominal yield point f_(y)=460 MPa and with a nominal failure stress off_(u)=530 MPa was selected. Furthermore, the web thickness t₀ wasincreased slightly in the connection region of the interlock strips 14,as compared with a standard straight sheet pile having the same nominalwidth.

In order to ensure that the tapered web 12 is deformed plasticallybefore the interlock strips 14 give way, the nominal failure load of theweb was limited to 85% of the guaranteed interlock tensile strength.This results in a web thickness t in the region of the central webportion 24 of:t>/f _(u)

t>9.6 mm  (2)

Finally, a minimum web thickness t of 9.5 mm was selected for thecentral web portion 24.

This minimum thickness t is constant with a width B in a central webportion 24, this width B advantageously amounting to at least 5% of theoverall width W of the web 12. This central web portion 24 with theminimum thickness t absorbs the plastic deformation of the web after theyield point is overshot. The larger the width B is, the greater is theplastic work capacity of the straight sheet pile, that is to say themore the web can expand in width before it ultimately fails. In order tobe able to easily roll the slightly thickened interlock strips 14 bymeans of an only slightly modified set of rolls, sufficiently wide webedges with an increased thickness t₀ should remain. Furthermore, itshould be noted in this respect that too large a width B may lead toinstabilities when the straight sheet pile is driven in. Moreover, it isalso important to limit the plastic deformation in order to avoid damageto the secondary structure. Beyond a defined deformation, the straightsheet piles should in this case avoid further load absorption, in orderthereby to initiate a shift operation. For these reasons, therefore, thewidth B in the central web portion 24 should not be too large andbasically should be no larger than 80% of the overall width W of the web12. Initial tensile tests also confirmed that even a width B ofapproximately 30-60 mm for the central web portion 24 with a minimumthickness t would seem to increase the plastic work capacity of thesheet pile 10 sufficiently for many applications. A substantially lowerplastic work capacity is achieved by means of a web having a thicknessthat decreases continuously as far as the center line 22 of the web 12,so that the web reaches its minimum thickness t only on the center lineof the web (that is to say, B≈0).

In the tapered portion 26 from the central web portion 24 having theminimum thickness t to the thickened web edges having the thickness t₀,the web 12 advantageously has a convexly cylindrical surface with aradius R₁ which has adjoining it towards the center line of the web aconcavely cylindrical surface with a radius R₂. The radius R₂ is in thiscase substantially larger than the radius R₁ and is larger by a multiplethan the nominal width L of the sheet pile.

It should be noted that the straight sheet pile 10 of FIG. 2 can berolled with only slight modifications by means of the same roll standwhich is used for rolling the standard webs with a constant webthickness. For this purpose, an existing pair of rolls, by means ofwhich normally straight sheet piles with a standard range are rolled,needs to be lathe-turned only slightly, which certainly requires nomajor investment.

For the purpose of a further explanation of the typical properties ofthe straight sheet piles according to the invention, the graph in FIG. 3shows representative load/displacement curves for three differentstraight sheet piles. These curves were recorded in path-controlledtensile tests according to prEN 12048. The test candidates differed fromone another only in the shape of the web and all had a steel quality S460 GP with a nominal yield point f_(y)=460 MPa and with a nominalfailure stress of f_(u)=530 MPa.

The curve 1 is the load/displacement curve for a connection of twosamples from a standard straight sheet pile with a constant webthickness of 13 mm. It can be seen that, although this connectionachieves a tensile load of more than 6000 kN/m, it starts to becomeunstable already with a relative displacement of 5 mm. The failure ofthe connection ultimately occurs due to a tearing-open of the interlockconnection.

The curve 2 is the load/displacement curve for a connection of twosamples from a straight sheet pile in which the thickness of the webdecreases continuously from a value of 13.5 m in the vicinity of theinterlock strips as far as the center line of the web and a minimumthickness of the web of 9.5 mm is achieved on the center line of theweb. It can be seen that this connection achieves a maximum tensile loadof 4500 kN/m, but that it becomes unstable only after a relativedisplacement of more than 7 mm. The failure of the connection is in thiscase preceded by a pronounced plastic displacement distance ofapproximately 5 mm. This plastic displacement distance thus amounts toapproximately 1% of the overall width of the straight sheet pile 10.

The curve 2 is the load/displacement curve for the connection of twosamples from a straight sheet pile according to FIG. 2 in which t₀=13.5mm, t₀=13.5 mm, t=9.5 mm and B=40 mm. This connection, too, achieves amaximum tensile load of 4500 kN/m. However, the failure of theconnection is preceded by a plastic displacement of almost 10 mm, sothat it can absorb relative displacement of almost 12 mm in the tensiledirection, without the opening of the interlock connection occurring.The plastic displacement distances in this case amount to 2% of theoverall width of the straight sheet pile 10.

Owing to their high plastic deformation capacity, straight sheet pilesaccording to the invention are pre-eminently suitable for use incofferdams which may be rammed by ships, which are to withstand theimpact of drift flotsam in spring tides and storm tides and/or which areto be erected in earthquake zones. The risk of the tearing-open of aninterlock connection and therefore the risk of a run-out of the fillingof a cofferdam cell is appreciably reduced by means of the straightsheet piles according to the invention.

Last but not least, the novel straight sheet piles in accordance withthe present invention are particularly useful because they can beproduced on an existing roll stand having an only slightly modified setof rolls. The necessary investment is therefore negligible, as comparedwith a new straight sheet pile with a constant web thickness and with amodified claw geometry.

1. A hot-rolled straight-web steel sheet pile, comprising: a webdelimited on each longitudinal side by an interlock strip, wherein theweb lies on an axis extending through said interlock strips and extendsbetween the interlock strip on each longitudinal side in a straightfashion without bends or curves; wherein said web has a rolled-in taperresulting in a reduced web thickness which is designed in such a waythat, in a tensile test of two samples from said sheet pile that areconnected by means of their interlock strips, said web is plasticallydeformed in the region of said reduced web thickness before a failure ofthe interlock connection can occur.
 2. The sheet pile according to claim1, wherein: a minimum tensile strength is guaranteed for said interlockstrips, and said web has a nominal failure load which is less than 90%of said minimum tensile strength of said interlock strips.
 3. The sheetpile according to claim 1, wherein: in a tensile test of the sheet pileloaded by means of the interlock strips, a plastic displacement distanceof at least 1% of the nominal width of said sheet pile is measured forsaid web.
 4. The sheet pile according to claim 1, wherein said web hastwo rolled-in tapered portions designed symmetrically with respect tothe center line of said web.
 5. The sheet pile according to claim 4,wherein said web has a central portion with a width and with a constantthickness, and this thickness is the minimum thickness of said web. 6.The sheet pile according to claim 5, wherein said web has an overallwidth and said width of said central portion amounts to between 5% and80% of said overall width of said web.
 7. The sheet pile according toclaim 6, wherein said width of said central portion has a value ofbetween 30 mm and 100 mm.
 8. The sheet pile according to claim 1,wherein said web has its maximum thickness in the connection region ofsaid interlock strips.
 9. The sheet pile according to claim 1, whereinthe thickness of said taper decreases continuously up to the center lineof said web, and the minimum thickness of said web is achieved on thecenter line of said web.
 10. The sheet pile according to claim 9,wherein said web has its maximum thickness in the connection region ofsaid interlock strips.
 11. The sheet pile according to claim 1, whereinsaid web has along each interlock strip a portion with a width and witha constant thickness, and this constant thickness is the maximumthickness of said web.
 12. The sheet pile according to claim 1, whereinsaid taper has a convexly cylindrical surface with a first radius, towhich adjoins, towards the center line of said web, a concavelycylindrical surface with a second radius, the second radius being largerthan the first radius and being larger than the nominal width of saidsheet pile.
 13. The sheet pile according to claim 1, which is designedin such a way that a minimum interlock tensile strength of at least 5500KN/m is guaranteed.
 14. The sheet pile according to claim 13, whereinsaid interlock strips comprise symmetrical thumb and finger interlocks.15. The sheet pile according to claim 14, wherein the symmetrical thumband finger of said interlock strips are located on opposite sides of theaxis.
 16. The sheet pile according to claim 1, wherein said interlockstrips comprise symmetrical thumb and finger interlocks.
 17. The sheetpile according to claim 16, wherein the symmetrical thumb and finger ofsaid interlock strips are located on opposite sides of the axis.
 18. Thesheet pile according to claim 1, wherein the straight web lies on theneutral axis of the sheet pile.
 19. The sheet pile according to claim 1,wherein the web extends between the interlock strip on each longitudinalside in a straight fashion without bends or curves.
 20. The sheet pileaccording to claim 1, wherein the taper is constructed and arranged toresult in a plastic displacement distance of at least 1% of the nominalwidth of the sheet pile before any portion of the sheet pile fails whenstressed in tension between the interlock strips.
 21. A hot-rolledstraight-web steel sheet pile, comprising: a straight web that lies onthe neutral axis of the sheet pile and has an overall width between twolongitudinal sides, rolled-in taper portions and a central portion ofthe web with a constant thickness a width that amounts to between 5% and80% of said overall width; and an interlock strip along each of said twolongitudinal sides of said web; wherein said central portion is designedin such a way that, in a tensile test of two samples from said sheetpile that are connected by means of their interlock strips, said web isplastically deformed in said central portion of said web before afailure of said interlock connection can occur.
 22. The sheet pileaccording to claim 21, wherein a minimum tensile strength is guaranteedfor said interlock strips, and said web has a nominal failure load whichis less than 90% of said minimum tensile strength of said interlockstrips.
 23. The sheet pile according to claim 22, which is designed insuch a way that a minimum interlock tensile strength of at least 5500KN/m is guaranteed.
 24. The sheet pile according to claim 21, wherein,in a tensile test of two samples from said sheet pile that are connectedby means of their interlock strips, a plastic displacement distance ofat least 1% of the nominal width of said sheet pile is measured for saidweb.
 25. The sheet pile according to claim 21, wherein said constantthickness of said central portion is the minimum thickness of said web.26. The sheet pile according to claim 21, wherein the straight web lieson an axis extending through said interlock strips.
 27. A straight-websheet pile for the construction of cellular cofferdams without internalanchoring, the straight-web steel sheet pile comprising: a straight webdelimited on each longitudinal side by an interlock strip, wherein thestraight web and interlock strips are constructed and arranged toconstruct a cellular cofferdam without internal anchoring, wherein thestraight web extends between the interlock strip on each longitudinalside in a straight fashion without bends or curves and wherein thestraight web and interlock strips are primarily stressed in tension inthe direction of an horizontal wall axis when assembled in the cellularcofferdam without internal anchoring; and a central portion of the webdelimited on each longitudinal side by tapered portions in the straightweb constructed and arranged such that, when the straight-web sheet pileis loaded in tension along the horizontal wall axis, the central portionplastically deforms at a lower tensile load than required to fail aninterlock connection by the interlock strips.
 28. The sheet pileaccording to claim 27, wherein the central portion is constructed andarranged to result in a plastic displacement distance of at least 1% ofthe nominal width of the sheet pile before any portion of the sheet pilefails in tensile loading when loaded in tension by the interlock strips.29. The sheet pile according to claim 27, wherein the central portionhas a width with a constant thickness that is the minimum thickness ofthe web.
 30. The sheet pile according to claim 29, wherein the web hasalong each interlock strip a portion with a width and with a constantthickness that is the maximum thickness of the web.
 31. The sheet pileaccording to claim 27, wherein the web lies on an axis extending throughthe interlock strips.
 32. A hot-rolled straight-web steel sheet pile,comprising: a web delimited on each longitudinal side by an interlockstrip, wherein the web extends between the interlock strip on eachlongitudinal side in a straight fashion without bends or curves; whereinsaid web has a rolled-in taper resulting in a reduced web thicknesswhich is designed in such a way that, in a tensile test of two samplesfrom said sheet pile that are connected by means of their interlockstrips, said web is plastically deformed in the region of said reducedweb thickness before a failure of the interlock connection can occur.33. A hot-rolled straight-web steel sheet pile, comprising: a straightweb having an overall width between two longitudinal sides and arolled-in taper portion and a central portion of the web with a constantthickness width that amounts to between 5% and 80% of said overallwidth; and an interlock strip along each of said two longitudinal sidesof said web, said web extending between said interlock strips in astraight fashion without bends or curves; wherein said central portionis designed in such a way that, in a tensile test of two samples fromsaid sheet pile that are connected by means of their interlock strips,said web is plastically deformed in said central portion of said webbefore a failure of said interlock.